Further study of the structures of bacterial steroid isomerases from Pseudomonas testosteroni and Pseudomonas putida (T-isomerase and P-isomerase) and the functional effects of various chemical modifications of their active sites is proposed. The site of the minor covalent attachment reaction which occurs during the 19-nortestosterone acetate dependent photoinactivation of T-isomerase will be identified using novel solid state affinity labeling technology under current development. Proton nmr studies of steroid - T-isomerase binding will be continued in order to identify resonances which are perturbed by bound steroid. Sequence analysis of P-isomerase will be continued, hopefully to completion. A method for specific linkage of peptides to insoluble supports via the C-terminal carboxyl will be further developed and applied to several test peptides.